This project investigates "locomotor stereotypy" exhibited by amphetamine- and scopolamine treated rats. Locomotor stereotypy is defined as repetition of a pattern of locomotion in an open field; that is, the rat frequently retraces its steps. Locomotor stereotypy is an important but little studied component of the behavioral response to amphetamine and scopolamine in rats. The ability to describe and quantify locomotor stereotypy provides a much more sophisticated tool for behavior analysis than is currently available. The health relatedness of the project lies in the widespread use of the behavioral effects of amphetamine in rats as a model of dopamine activity in the brain. For example, a drug which blocks the behavioral effects of amphetamine may be a useful antipsychotic; a neuropeptide which alters the behavioral effects of amphetamine may influence dopamine neurotransmission in some way, and so on. The health relatedness of the project also lies in the increasing similarities of the behavioral effects of amphetamine and scopolamine (both produce hyperlocomotion, locomotor stereotypy, and elevated mood) and in the possible interactions between dopamine and acetylcholine which produce them. The immediate goal of the proposed research is to begin to determine the neurotransmitters and the anatomical sites important in locomotor stereotypy. The specific aims are to determine the ability of muscarinic cholinergic antagonists to produce locomotor stereotypy; to determine the effects of dopamine antagonists (D1/D2, atypical/typical) on amphetamine- and scopolamine-induced locomotor stereotypy; to determine the ability of D1 and D2 direct dopamine agonists to produce locomotor stereotypy; to localize areas of the brain involved in amphetamine- and scopolamine- induced locomotor stereotypy using microinfusions. These experiments will indicate whether amphetamine- and scopolamine-induced locomotor stereotypy are produced by similar mechanisms and whether locomotor stereotypy and more classic behaviors are mediated by different neurochemical mechanisms. Once the neurochemical basis of locomotor stereotypy is described, locomotor stereotypy can be used as a behavioral model for interactions between many neuroactive agents.